WH Smith has also bought the Wild Cards and Gifts chain in Australia, in January which operates 50 small gift shops. Photograph: Philip Toscano/PA

WH Smith is moving into operating franchise stores for other retailers including Marks & Spencer as the books to paperclips retailer develops a growing portfolio of brands.

The company has signed a deal to operate Mr Simms Olde Sweet Shoppe stores in travel hubs such as train stations while it plans to open at least two more M&S Simply Food outlets in hospitals this year on top of four already operating.

The retailer also bought the Wild Cards and Gifts chain in Australia, in January which operates 50 small gift shops in travel hubs via franchise partnerships. That comes on top of WH Smith's own Funky Pigeon gift and card business which operates online and via small stores.

"If something comes along that creates value for shareholders then we'll look at it," said Steve Clarke, chief executive.

WH Smith said it would increase its interim dividend by 15% to 10.8p per share after revealing a 3% rise in pre-tax profits to £69m for the half year to the end of February. Profits were boosted by cost savings and efficiencies as sales slid 4% in total while underlying sales slipped 1% at travel stores and 6% on the high street.

Clarke said WH Smith had seen its first rise in underlying sales at airports since 2008 but expected the market to remain subdued. He said: "We still have a decent pipeline of new [cost saving] initiatives we're trying. We haven't run out of ideas."